GALACTIC LENS

   This term, from ASTRONOMY, makes frequent appearance in sf. It refers to the fact that our Galaxy is (like many others) approximately lens-shaped - it is a disc containing spiral arms, but like a lens it has a central bulge. Our own position in the Galaxy is quite a long way from the core; when we look towards the centre of the "lens", the direction in which the stars are clustered most thickly, we see the so-called Milky Way. Towards the outer rim of the "lens", stars are comparatively sparse, not only in terms of the numbers lying in our line of sight but also in fact. Many sf writers have set stories on planets circling such stars. Such worlds were dubbed Rim Worlds by A. Bertram CHANDLER, and the term (often as "Rimworld") has since become commonplace in sf.

   PN